The present invention relates to an anti-reflection film having anti-glare property, and a polarizing plate using the same. Further, the present invention relates to an image display device, such as a liquid crystal display device, using the anti-glare and anti-reflection film or the polarizing plate.
An anti-reflection film having anti-glare property is generally disposed on the outermost surface of a display, which decreases the reflectance by using the principle of optical interference, to prevent the capture of an image or the decrease of contrast due to reflection of external light, in an image display device, such as a cathode ray tube display device (CRT), a plasma display panel (PDP), and a liquid crystal display device (LCD).
However, in the anti-reflection film provided with only a hardcoat layer and a low-refractive-index layer on a transparent support, the low-refractive-index layer must be made to have a sufficiently lowered refractive index, to lower the reflectance. In order to decrease the average reflectance of, for example, an anti-reflection film, in which use is made of triacetyl cellulose, as a support, and a UV-cured coating of dipentaerythritol hexaacrylate, as a hardcoat layer, to 1.6% or less, in a wavelength range between 450 nm and 650 nm, the refractive index of such a low-refractive-index layer must be 1.40 or less.
Examples of materials having a refractive index of 1.40 or less include inorganic materials, such as magnesium fluoride and calcium fluoride, and organic materials, such as fluorine-containing compounds having a high fluorine content. However, these fluorine-containing compounds lack in cohesive power, thereby insufficient in abrasion-resistance needed for the film layer disposed on the outermost surface of a display. It is therefore conventionally necessary to use a compound having a refractive index of 1.43 or more, to insure sufficient resistance to damage (abrasion).
JP-A-7-287102 (xe2x80x9cJP-Axe2x80x9d means unexamined published Japanese patent application) describes that the reflectance is reduced by making the refractive index of the hardcoat layer high. However, a hardcoat layer having such a high refractive index causes uneven color on the film, because of a large difference in refractive index between the hardcoat layer and a support, and the wavelength dependency of the reflectance is thereby largely fluctuated resultantly.
Further, JP-A-7-333404 discloses anti-glare and anti-reflection films that excel in properties of gas barrier, anti-glare, and anti-reflection. However, these films need a silicon oxide film formed by a CVD method, which is poor in productivity, as compared to a wet coating method, in which a film is formed by applying a coating solution. In addition, the anti-reflection performance of a thus-obtained anti-glare and anti-reflection film is unsatisfactory.
On the other hand, it is desired to make the pixel size as small as possible in an image display device, thereby improving the quality of display (attaining highly-fine definition of an image). Therefore, there is a need to develop an anti-glare and anti-reflection film that can effectively meet this need.
The present invention is an anti-glare and anti-reflection film that comprises a transparent support having thereon, an anti-glare layer and at least one low refractive index layer superposed in this order, wherein an average mirror (specular) reflectance at an incidence of 5 degrees in the wavelength region of 450 nm to 650 nm is 1.2% or less.
Further, the present invention is a polarizing plate that comprises a polarizing layer and two protective films therefor, at least one of said protective films being the above-mentioned anti-glare and anti-reflection film.
Furthermore, the present invention is an image display device, in which the above-mentioned anti-glare and anti-reflection film or the above-mentioned anti-glare and anti-reflection polarizing plate (i.e. its anti-reflection layer), is disposed as the outermost surface layer at the display side.